Attrition scrubbers are used for cleaning contaminated particulate material, in particular for delaminating clay from sand particles. The particulate material is typically delivered to the attrition scrubber as a liquid slurry having water content of between 20% and 25% by weight. Typically attrition scrubbers comprise several attrition cells, each cell having two or more sets of impellers mounted on a common shaft driven by a respective drive motor, typically an electric motor, such that the movement of the blades of the impellers cause intense scrubbing, polishing and disintegration of the particulate material located within each cell.
A problem with known attrition scrubbers is that the water content of the slurry must be carefully controlled to ensure efficient operation of the attrition scrubber. If too much water is present the slurry may not be sufficiently dense for the attrition process to take place. If the water content is insufficient the load applied to impellor drive motors and to the impellor blades may cause damage to such components.